Signal plug for engine failure warning systems



Oct. 5, 1948.

SIGNAL PLUG FOR ENGINE FAILURE WARNING SYSTEMS Filed Aug. 1, 1947 FIG-.- 1.

INVENTUR.

vE. w. BouRNE, JR 2,450,630 l dPatented Oct. 5, 1948 SIGNAL PLUG FOR ENGINE FAILURE WARNING SYSTEMS Edmund W. Bourne, Jr., Utica, N. Y. application aufm 1 1w, serial No. 165,363

The invention covered herein relates to engine failure warning systems ci the type disclosed in copending application Serial No. 004,400, tiled July 1l, 1945, now Patent No. 2,429,920, issued October 28. 1947, involving the provision oi' a plug in the oil circulating system,v carrying terminals separated by a gap adapted to be bridged by metallic particles in the oil to close a circuit for warning a pilot, in the case of aircraft engines, of the existence or approach of dangerous conditions.

Magnetizing means are provided for attracting magnetic particles across the gap of the plug. As pointed out in that application, such magnetizing means may be either of the electromagnetic or of the permanent magnet type.

For reasons of greater simplicity, low cost and less wiring, the permanent magnet form of plug may be preferred. l

The present invention is directed to this permarient magnet form of plug. Thecbjects of tle invention, as will be clear from the above, are to provide a signal plugwhich will be of low cost, simple construction, which will require only a single wire for the signalling or warning circuit which it controls and which generally will be practical and desirable for the purposes outlined.

One particular object of the invention is to provide a signal plug which will be of such design that it may be substituted in place of thegdrain plug usually present in engines such as should be protected by devices of this sort.

Other important objects attained by the invention will appear as the specification proceeds.

The drawing accompanying and forming part vof the specification illustrates one of the present commercial embodiments of the invention. Structure, however, may be modied and changed as regards this immediate illustration, all within the true spirit and broad scope of the invention as herein defined and claimed.

Fig. 1 in the drawing is a brolmn sectional view illustrating one of the signal plugs screwed into the drain hole opening of an engine crank case; Fig. 2 is a broken end elevation of the same Darts.

In the drawing a portion of an engine crank case is indicated at 3. having a screw threaded drain opening l.

The signal plug of this invention `comprises ay hollow tubular shell 5 screw threaded to be engaged in the drain hole iitting and carrying at its inner end a center disc-like electrode or terminal 'l 0 spaced by an annular gap 1 from the surroundingr rim of the shell constituting. in effect. a companion. outer annular electrode 8,.

The center, disc-like electrode 6 -is of magnetic material and is fixed on vthe inner end of a powerfulpermanent magnet 9.

3 Claims. (Cl. 200-52) The outer Vend of magnet 9 is ilxed to a flanged cup or cap I0 of magnetic material in close magnetic relation to the shell but electrically insulated therefrom as by a thin layer of insulation II.

To obtain the greatest possible magnetic force, the permanent magnet may be made of "Alnico V. It may be of cylindrical or other such symrnetrical form. It is shown made in truncated, conical shape and arranged with the smaller. tapered end inward." This provides a wide, ilrm base for the .outer end of the magnet on the mounting cup orcollar I0 and a maximum of space between the magnet and surrounding shell, toward the inner end of the plug and beneath the overstanding disc 6 forming the inner electrode.

The three magnetic'pieces 9 and I0, maybe secured together in various ways. One practical method is that shown and involving a pin or stud I2 of brass or the like, extending through all three and having a flange I 3 at the outer end in abutment with the magnetic head I0 and ritjeted at its inner end over the disc 6, as indicated vat I4.

This rivet stud I2 is' shown as having a reduced terminal pin extension I5 at its outer end for engagement by the'couplingof a signal cord circuit wire.

The riveted magnet assemblyI described is shown as seated in the plug shell on top of a screw collar I8 having a flange I1 seated on an internal ange I8 in the outer end of the screw Ashell 5.

The insulating layer I I is shown as extending in between the opposing faces of the magnet head and screw collar I6.

The center electrode 6 with its terminal extension I5, is thus insulated from the body. or shell 5 of the plug and from the surrounding structure. The outer magnetic head I0 of the magnet, however, is in close, magnetically coupled relation with the surrounding screw shell, and hence able to strongly polarize the inner end of the shell at 8 in opposition to the polarity of the disc electrode 6 at the inner end of the magnet. Consecally insulating medium I9 such as Bakelite compound or sealing wax.

-The inner surface of the screw shell is shown as recessed at 20 to enable the insulating filling I9 to key into the shell and mechanically interlock as well as seal the parts togethen The warning or signal circuit may be made up y3 as indicated, with an of a single wire cable 22 held engaged over the terminal pin I by screw bushing 2l, said'cable being connected with a light, horn or other sultable warning signal 24 energized, when the gap 1 is bridged by metallic particles in the oil. from a battery 26 or other source of electrical energy.

The making of these signal plugs the same size as crank case drain plugs ordinarily'employed,

' enables a warning system of the character disclosed in this and the companion patent application to be applied to an aircraft or other power plant by simply removing the regular drain plug and replacing it with the signal plug, and connecting the lead from the signal plug to a warning or other ,desired signal or protective device. The system will then effectively warn of the presence of metal cuttings, parts or particles in the lubricating oil, whether magnetic or non-magnetic. Magnetic particles will be drawn into position across the magnetic gap 1 to close the signal circuit and non-magnetic particles will have the same effect by bridging across the gap between the electrodes 8 and l, either by reason of circulation of theoil or by settling in such position.

These plugs will ordinarily be located in a low part of the system where precipitation of any foreign medium will promptly occur.

The plug is of simple, durable structure, capable of withstanding hard service and with no parts to get out of order. The cost of production is low since there are few parts and little machining to be done. The Alnico V magnet unit 9 is of relatively small size and hence lowcost and the only work that need be done upon it ordinarily would be to grind or otherwise face oif the opposite ends to make close nt with the electrode disc 6 and end head I0. The pin I2 serves the double function of riveting these parts together and of providing an integral external terminal pin I5.

The thin layer II of insulation about and beneath the end of the magnetic head III may be of hardsheet bre or like material and may be all in one piece in the form of an appropriately shaped cup, or be in several pieces, such as one piece in the form of a band about the head and a second piece in the form of a washer beneath the head.

The parts are readily put together as by first assembling the magnet unit made up of the pieces B, 9 and I0, connected by the rivet pin I2, and then after dropping the terminal sleeve I6 in the screw sleeve 5 and the magnet unit on top of that, with the interposed insulation II, pouring in the thermosetting potting compound I9 to seal and permanently secure the whole While the plug shell 5 is of magnetic material to carry the magnetic circuit back or inward to the disc electrode 6, the terminal `or attachment sleeve I6 need not be of magnetic material since its primary and practically only function is to enable a mechanical coupling of the signal cable to the plug.

What is claimedis: 1. A signal plug for an engine failure warning system comprising a screw shell for engagement in a crank case drain opening or the like, said screw shell being of magnetic material, a permanent magnet mounted in fixed relation in said screw shell and electrically insulated therefrom, an electrode disc at the inner end of said permanent magnet separated from the screw shell by a magnetic gap, the outer end of said permanent magnet being electrically insulated from but in magnetically coupled relation with said magnetic electric plug 2| at the end :,esaeso y screw shell and a terminal at the outer end of said screw shell electrically connected with said electrode at the inner end of said permanent magnet and including a terminal pin extending inwardly through said permanent magnet to said electrode, a magnetic head atthe outer end of said permanent magnet and providing the magnetic coupling between the outer end of the permanent magnet and the screw shell, said terminal pin being riveted ,to hold said electrode to the inner end of the permanent magnet and said magnetic head to the outer end of the same and said riveted pin having a terminal extension at the outer end of the same for connection with an externalwarning or signal circuit.

2. A signal plug of the character disclosed comprising a plug shell' for mounting in a drain plug opening or the like, said shell having an internal flange at the outer end of the same. a terminal sleeve having a ilange seated on the flange of said plug shell, a magnetic head seated on the inner end of said terminal sleeve, electrical insulation interposed between said magnetic head, terminal sleeve and plug shell, a permanent magnet seated on said magnetic head, an electrode disc on the inner end of said permanent magnet and spaced from the inner end of the plug shell to provide therewith a magnetic gap, a pin extending from said electrode disc throug said per# marient magnet and through said magnetic head and riveted to hold said three parts together, said riveted pin having at the outer end oi' the same a terminal pin extension for connection with an external warning circuit.

3. A signal plug for an engine failure warning systemcomprising a plug shell for mounting in a drain plug opening or theA like, a permanent magnet mounted in fixed relation in said shell` spaced from the surrounding wall of said shell and having an electrode forming element at the inner end of the same spaced from the inner end of the shell a distance to form a magnetic gap, electrical insulation between the outer end of said magnet and shell and lling the space between the a flange about the rim of the same rigidly held in the plug shell, said electrical insulation including insulation between said ilanged head and shell and said terminal extending through said flanged head to said electrode element at the inner end of the magnet.

EDMUND W. BOURNE, JR.

REFERENCES CITED The following references are of record in the tile of this patent:

UNITED STATES PATENTS Number Name Date 570,496 Osborn Nov. I3, 1896 692,217 Sundh Jan. 28, 1902 1,362,992 Haywood et al Dec. 21, 1920 2,252,222 Van Os Aug. 12, 1941 2,358,612 Acker Sept. 19, 1944 2,420,177 Krall May 6, 1947 2,429,920 Bourne Oct. 28, 1947 

